Catalytic Efficiencies of H2O, D2O, NO, and HCl in the Vibrational Relaxation of HF and DF

Abstract

The catalytic efficiencies of H2O, D2O, NO, and HCl in the vibrational relaxation of HF and of NO in the vibrational relaxation of DF were investigated over the temperature and total pressure ranges of 1000 to 4100°K and 0.1 to 0.3 atm, respectively. Measurements were made in an Ar diluent behind incident shock waves. The extent of vibrational excitation in HF was determined as a function of time by continuously monitoring the infrared emission intensity at 4150 ± 200 cm−1. Water appears to relax HF principally by means of a direct transfer of vibrational energy (V–V) between the collision partners. Furthermore, its collisional efficiency was found to be in fair agreement with the results reported by others for the analogous process of HCl relaxation by H2O. Nitric oxide was found to be at least an order-of-magnitude more efficient as a collision partner in the vibrational relaxation of HF than is known for either of the molecules N2 or O2. A small amount of data regarding the effect of HCl upon the vibrational relaxation of HF was collected. Within the temperature range considered, its catalytic efficiency was found to be comparable to that of HF itself.